1. Field of the Invention
The present invention relates to powders of amino acids, which is a microfine or granulated amino acid powder containing trehalose. The present invention further relates to methods for producing such powders.
2. Discussion of the Background
Amino acids, amino acid salts, and amino acid derivatives (simply referred to as amino acids hereinafter) are widely used in medical diets for nutrition supplements, disease-specific amino acid preparations for oral administration and infusion for subject patients with renal impairment and liver disorders, infantile nutritious compositions, diet food materials, health foods, and functional foods. Further, amino acids are used in cosmetics and in veterinary preparations for dosing to animals, after being mixed in feeds and the like.
Trehalose, when contained in amino acids, not only serves as a saccharide nutrient but also suppresses the bittern taste of amino acids, advantageously, without any occurrence of the Maillard reaction (browning reaction). Therefore, the presence of trehalose therein is recommended. Specifically, those formulations described below are known.
For example, trehalose-coated (film) powders of amino acids are known, and may be prepared by one of the following methods. In a first method, a binder is added to a powder of amino acids in mixture to prepare granules by an extrusion granulation process, and the granules surfaces are then coated with trehalose as a coating material by fluid granulation. In a second method, trehalose and a binder are added to a powder of amino acids in mixture for coating by fluid granulation, and spraying an aqueous ethanol solution over the resulting coated powder for granulation (see, JP-A-6-227975).
Furthermore, an amino acid infusion containing trehalose and having the same effects as described above is also known (see, JP-A-6-70718).
Also known are amino acid food products containing trehalose, which are adjusted to a pH 3.0 to 6.0 by the addition of sour agents such as citric acid so as to prevent flavor deterioration due to heating of the amino acid, or flavor modification or color modification of the amino acid during long-term storage. The test results of heating the hydrous amino acid-containing solution are disclosed (see, JP-A-2000-4836).
As compositions for use in the suppression of blood amino acid variation following vigorous athletic motion, a hydrous solution of a composition of amino acids and sugar is disclosed, which contains at least 13 types of amino acids and trehalose. The hydrous solution is said to be effective for the improvement of athletic potential and the amelioration of fatigue (see, JP-A-2000-72669).
As described above, various findings exist about amino acid compositions containing trehalose, but only JP-A-6-227975 describes such a powder. Further, no amino acid powder with a high oral meltability, high solubility, and masked taste is known. In particularly, there remains a need for a dry power of a branched amino acid and a slightly soluble amino acid, which has improved oral meltability and solubility and suppressed bitterness.
As production methods of dry powders, meanwhile, the spray drying method, hot-air drying method, and freeze-drying method are known. Among them, the spray drying method is capable of producing microfine particles, and is a dry method for recovering a dry powder of spherical and spherical shell-shaped powder, by dispersing a solution or a particle slurry into the form of microfine particles in hot air, where the spray method uses pressure nozzle, rotating disk, and two-fluid nozzle and the like. In many cases, the mean particle size of the dry powder is about 20 μm to 500 μm (see, Handbook of Chemistry and Engineering, revised sixth edition, p. 770, p. 780 (1999), issued by Maruzen), while in the pharmaceutical field, a production example of microfine particles of 10 μm or less is introduced (see, JP-A-9-235238, JP-T-10-500672, and JP-A-11-114027). In recent years, a four-fluid nozzle has been developed, which has enabled mass-scale spray drying with a liquid droplet having a mean particle size of several micrometers (see, Chemical Apparatus, pp. 60-65 (June, 2000), and Japanese Patent No. 2,797,080, and JP-A-2002-17337, etc.).
Similar to the powders containing microfine amino acids, an inhalation dry composition containing the pharmacologically active component, interferon, as the essential component and containing a hydrophobic amino acid selected from leucine, isoleucine, and valine at 60% or more to less than 100% (mean particle size (volume-based distribution) of 0.1 μm or more to 10 μm or less) is disclosed for the purpose of avoiding the deliquescence of the inhalation dry composition, when left at a high humidity (see, JP-A-9-235238). In Example 2 of JP-A-9-235238, a dry particle powder is obtained as a control, by preparing a solution containing 3.5 g of isoleucine, 0.7 g of serum albumin, 695.8 g of deionized water, and 300 g of ethanol for spray drying, and then spraying the resulting solution with a spray dryer (aerodynamic mean particle size of 0.9897 μm). However, this Example does not include any description of oral meltability, solubility, and taste masking.
Moreover, it is also desired that the production of powders of amino acids by spray drying in such manner can be done on a mass scale; that the quality can be maintained; and that the oral meltability and solubility of the resulting powders are great. Accordingly, there remains a need for any improved process so as to satisfy these properties.